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  <div class="section" id="module-Bastion">
<span id="bastion-restricting-access-to-objects"></span><h1>29.2. <a class="reference internal" href="#module-Bastion" title="Bastion: Providing restricted access to objects. (deprecated)"><tt class="xref py py-mod docutils literal"><span class="pre">Bastion</span></tt></a> &#8212; Restricting access to objects<a class="headerlink" href="#module-Bastion" title="Permalink to this headline">¶</a></h1>
<p class="deprecated">
<span class="versionmodified">Deprecated since version 2.6: </span>The <a class="reference internal" href="#module-Bastion" title="Bastion: Providing restricted access to objects. (deprecated)"><tt class="xref py py-mod docutils literal"><span class="pre">Bastion</span></tt></a> module has been removed in Python 3.</p>
<p class="versionchanged">
<span class="versionmodified">Changed in version 2.3: </span>Disabled module.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The documentation has been left in place to help in reading old code that uses
the module.</p>
</div>
<p>According to the dictionary, a bastion is &#8220;a fortified area or position&#8221;, or
&#8220;something that is considered a stronghold.&#8221;  It&#8217;s a suitable name for this
module, which provides a way to forbid access to certain attributes of an
object.  It must always be used with the <a class="reference internal" href="rexec.html#module-rexec" title="rexec: Basic restricted execution framework. (deprecated)"><tt class="xref py py-mod docutils literal"><span class="pre">rexec</span></tt></a> module, in order to allow
restricted-mode programs access to certain safe attributes of an object, while
denying access to other, unsafe attributes.</p>
<dl class="function">
<dt id="Bastion.Bastion">
<tt class="descclassname">Bastion.</tt><tt class="descname">Bastion</tt><big>(</big><em>object</em><span class="optional">[</span>, <em>filter</em><span class="optional">[</span>, <em>name</em><span class="optional">[</span>, <em>class</em><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><big>)</big><a class="headerlink" href="#Bastion.Bastion" title="Permalink to this definition">¶</a></dt>
<dd><p>Protect the object <em>object</em>, returning a bastion for the object.  Any attempt to
access one of the object&#8217;s attributes will have to be approved by the <em>filter</em>
function; if the access is denied an <a class="reference internal" href="exceptions.html#exceptions.AttributeError" title="exceptions.AttributeError"><tt class="xref py py-exc docutils literal"><span class="pre">AttributeError</span></tt></a> exception will be
raised.</p>
<p>If present, <em>filter</em> must be a function that accepts a string containing an
attribute name, and returns true if access to that attribute will be permitted;
if <em>filter</em> returns false, the access is denied.  The default filter denies
access to any function beginning with an underscore (<tt class="docutils literal"><span class="pre">'_'</span></tt>).  The bastion&#8217;s
string representation will be <tt class="docutils literal"><span class="pre">&lt;Bastion</span> <span class="pre">for</span> <span class="pre">name&gt;</span></tt> if a value for <em>name</em> is
provided; otherwise, <tt class="docutils literal"><span class="pre">repr(object)</span></tt> will be used.</p>
<p><em>class</em>, if present, should be a subclass of <a class="reference internal" href="#Bastion.BastionClass" title="Bastion.BastionClass"><tt class="xref py py-class docutils literal"><span class="pre">BastionClass</span></tt></a>;  see the
code in <tt class="file docutils literal"><span class="pre">bastion.py</span></tt> for the details.  Overriding the default
<a class="reference internal" href="#Bastion.BastionClass" title="Bastion.BastionClass"><tt class="xref py py-class docutils literal"><span class="pre">BastionClass</span></tt></a> will rarely be required.</p>
</dd></dl>

<dl class="class">
<dt id="Bastion.BastionClass">
<em class="property">class </em><tt class="descclassname">Bastion.</tt><tt class="descname">BastionClass</tt><big>(</big><em>getfunc</em>, <em>name</em><big>)</big><a class="headerlink" href="#Bastion.BastionClass" title="Permalink to this definition">¶</a></dt>
<dd><p>Class which actually implements bastion objects.  This is the default class used
by <a class="reference internal" href="#module-Bastion" title="Bastion: Providing restricted access to objects. (deprecated)"><tt class="xref py py-func docutils literal"><span class="pre">Bastion()</span></tt></a>.  The <em>getfunc</em> parameter is a function which returns the
value of an attribute which should be exposed to the restricted execution
environment when called with the name of the attribute as the only parameter.
<em>name</em> is used to construct the <a class="reference internal" href="repr.html#module-repr" title="repr: Alternate repr() implementation with size limits."><tt class="xref py py-func docutils literal"><span class="pre">repr()</span></tt></a> of the <a class="reference internal" href="#Bastion.BastionClass" title="Bastion.BastionClass"><tt class="xref py py-class docutils literal"><span class="pre">BastionClass</span></tt></a>
instance.</p>
</dd></dl>

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